The gillungs - waterbreathing, genetically modified humans - are thriving. They've colonised riverbanks and ports long since abandoned to the rising seas and the demand for their high-efficiency technologies is growing fast.

But as demand grows, so do fears about their impact on both norm businesses and the natural environment.

Then, a biohazard scare at Sinkat, their colony on the Thames, fuels the opposition and threatens to derail the gillungs' progress. But was it an accident, or was it sabotage?

DCI Sharon Varsi has her suspicions, but her investigations are compromised by family ties. And now there is a new threat: Zavcka Klist is about to be released from prison - and she wants her company back.